Ultrawide, 75 nm 3 dB gain-band optical amplifier utilizing erbium-doped fluoride fiber and Raman fiber

Summary form only given. Wideband optical amplifiers are the key devices to enlarge the capacity of WDM transmission systems. Several approaches have been investigated to broaden and flatten the gain band of fibre amplifiers, including combining a gain-flattened erbium-doped silicate fiber amplifier (EDSFA) with Raman amplification in the transmission fiber. This approach is quite effective to extend the gain band to longer wavelengths because the Raman gain counterbalances the decrease in the EDSFA gain. We achieve the extremely large 3-dB gain bandwidth of 75 nm (1531-1606 nm) with a novel configuration. A wideband and gain-flattened erbium-doped fluoride fiber amplifier is combined with an internal Raman amplifier using a high-NA germano-silicate fiber (Raman fiber). Error-free operation in a WDM (9/spl times/2.5 Gbit/s) transmission is confirmed in an in-line amplifier configuration.